In one aspect this invention relates to ballistic armor structures. More particularly, this invention relates to a ballistic armor which is conformable to a wide variety of vehicles or structures.
The use of ceramics and ballistic cloth as part of ballistic protective armor systems is well-known because of the light weight of these materials as compared to steel and other solid metallic armor. Ceramics are distinguished by a high hardness and very rigid structure. When used for ballistic protection, it is essential that the ceramic chosen be able to withstand the substantial shock load caused by an incident projectile and yet have some deformation protection. A typical ceramic armor structure has a ceramic material on its outer surface designed to withstand the shock of an incoming projectile. It is common to provide a fibrous or metal backing material behind the ceramic to support and withstand the deformation of the ceramic as it is impacted. In such a structure, the ceramic component will exhibit brittle breaking behavior. When the ceramic material receives a focused strike which initiates a crack, the ceramic material will undergo continuous cracking or crazing throughout its contiguous volume. Thus, a ceramic piece is effectively destroyed over its contiguous volume when struck by a projectile having sufficient energy to initiate cracking.
This problem is ameliorated by reducing the size of the contiguous portions of the ceramic, as by mounting small ceramic segments or plates over the entire face of the flexible backing material. This will minimize the surface area left unprotected when a single segment or plate is destroyed. Generally, for smaller sized vehicles, such as light trucks, ceramic plates on the order of 1 square inch have been found to provide a high degree of protection. Use of such small plates minimizes the damage to the overall structure from the incursion of an individual projectile and the associated destruction of one or two plates. Thus, multiple projectiles can be stopped by such a mosaic structure of ceramic segments or plates, the remaining danger being when numerous rounds repeatedly strike the same small area. For larger vehicles such as military combat vehicles, larger ceramic segments or tiles, of a size on the order of 2-3 square inches, provide effective protection from the larger projectiles normally faced by such vehicles. In such bigger vehicles, the larger ceramic tiles are generally thick enough to withstand multiple smaller projectiles without losing integrity.
While ceramic materials provide extremely good protection, the production of such protective mosaic structures, made up of such small ceramic segments or tiles, is extremely costly. Thus ceramics alone are not feasible as a protective means for a large surface in most applications. Furthermore, such structures are produced as plate mosaics, i.e., shaped collections of smaller ceramic tiles sized and shaped to overlay specific vehicle areas while mating with specific edges of complementary armor sections. Thus, such plate mosaics must be manufactured to a rigidly predetermined shape. This makes it difficult or impossible to transfer or otherwise remove armoring plate mosaics from one vehicle and place this armor on a vehicle other than the vehicle type for which a particular plate mosaic was manufactured.
There are a number of considerations to be examined when generating a ballistic structure, especially for mobile applications. A primary consideration is weight. Protective ballistic armor for heavy, mobile military equipment, such as tanks or large ships is a well developed art. Such armor usually comprises a very thick layer of alloy steel which provides protection against most heavy and explosive particles. Such vehicles or vessels are frequently capable of selectively adding further armor protection when they are deployed in combat zones. If such armor protection can be made more effective, the weight of the heavy armor could be reduced while still allowing the armor to defeat projectiles of comparable threat levels. Reduction of armor weight, even for heavy equipment supplied with large prime movers, is an advantage since it reduces the strain on all vehicle components and reduces operating costs. For these same reasons, current heavyweight armor is also less desirable for the light weight tactical vehicles which form the majority of any military vehicle fleet. Performance of tactical vehicles, such as heavy trucks, light trucks, and support vehicles is substantially compromised by steel panels having a thickness of more than a few millimeters because of the extreme weight each millimeter of steel armor adds to vehicle weight. For example, in the case of a light truck, steel armor sufficient to stop rifle projectiles can degrade performance on a hill grade to such an extent that the truck can only achieve the speed of a person walking.
Despite such shortcomings, armor for light vehicles is expected to prevent penetration from the threats posed by the common 7 mm military rifles and shrapnel from improvised explosive devices. In today's modern warfare, armor piercing projectiles even from military rifles represent a substantial threat and would require a relatively thick steel armor, typically of more weight than a light vehicle can carry.
Another consideration for military vehicles is cost. Overly complex armor arrangements, particularly those that depend upon laminated synthetic fibers consolidated using sophisticated resins and manufacturing techniques, can make manufacture of armor prohibitively expensive for large fleets of small vehicles.
A third consideration in armor design is adaptability; most ceramic and metal armors are essentially flat rigid plates and have little, if any, conformability. Manufacture of complex or conformable shapes using metal or laminated fibers which allow the resulting armor sub-components to be inserted into existing voids in a vehicle is nonexistent.
Yet another consideration in ceramic structures is the fact that ceramic plates are brittle and subject to fracture in handling and manufacturing which results in waste and additional cost.
It is an object of this invention to provide a conformable, self-healing ballistic structure which is effective against standard military projectiles and which can be readily attached to more than one type of vehicle.
It is a further object of the invention to provide a ballistic panel which is effective in resisting a plurality of projectiles impacting on the same general area.